Method of and means for determining the inclination of well pipes



Jue 19, 1962 C J. MCWHORTER METHOD OF AD MEANS FOR DETERMINING THEINCLINATION 0F WELL. PIPES Filed June 25, 1959 j fa/A ATTR/VEY June' 19,1962 c. J. MowHoRTER 3,039,544

METHOD OF AND MEANS FOR DETERMINING THE INCLINATION oF WELL PIPEs 2Sheets-Sheet 2 Filed June 25, 1959 Cu//en d M C W/mr fer INVENToR.

Afro/Mfr l United States Patent() 3,039,544 METHOD F AND MEANS FORDETERMINING THE INCLINATION 0F WELL PPES Cullen J. McWhorter, Houston,Tex., assignor to Houston Oil Field Material Company, luc., Houston,Tex., a

corporation of Delaware Filed June 25, 1959, Ser. No. 822,903 Claims.(Cl. 175-45) This invention relates to `a method of and apparatus forlogging wells, and more particularly to a method of determiningvariations in the inclination `of a well pipe for the purpose oflocating the point at which the pipe is stuck in a. Well, and to animproved inclino-meter for use in carrying out such a method.

In the drilling and operation of wells, such as oil and gas wells, it iscustomary to produce a Well bore by the use of a tubular drill string,having at its lower end a drill which is rotated with the string, thestring being usually of somewhat smaller external diameter than thediameter of the bore, and drilling Amud being circulated through thestring and through the bore outside of the string during lthe drillingoperation to lubricate the drill `and to carry away the cuttings formedthereby. The bore of a well produced in this manner may deviatesubstantially from the vertical yand in wells of substantial depth suchdeviation frequently takes place in different directions so that thebore is curved at various locations. Under some circumstances, such aswhen the drilling takes place in inclined formations, or 'whenalternately soft and hard formations are encountered, the drill may bedeflected in a manner to produce relatively sharp curves or bends,sometimes referred to as dog legs.

ln carrying out well drilling or other operations in wells the drillstern or other well -pipe lwill follow generally the curvature orinclination of the bore and when the well pipe is substantially smallerin diameter than the bore, which is usually the case, the pipe engagesthe wall of the bore at various locations throughout the length of thebore, so that the inclination of the pipe varies and is different fromthe inclination of the bore at some locations and may even assume asomewhat spiral shape.

It is often desirable to determine the inclination of the well bore, `orof the drill stem or other pipe therein, such `as the well casing ortubing, especially for the purpose of locating a dog leg or otherirregularity in the bore likely to interfere with the insertion orwithdrawal of the well pipe, or to locate the point at which the drillstem has become stuck in the Well due -to caving of the formation,settling of the drilling mud, or'from other causes.

Heretofore, in attempting to locate the point at which a well pipeshould be disconnected or cut oif, when such a pipe has become Stuck ina well, it has been customary to make use of instruments of the straingage type, which may be lowered into the well pipe and held stationarytherein while the stress or strain on the pipe is varied to indicate bydeformation of the pipe whether the pipe at a particular location isfree or stuck. By this method it is possible to locate within roughlimits the por-tion of the pipe which is stuck and the portion which isfree by relatively few readings, but this method has the disadvantagethat it is necessary to make a separate test at each of a large numberof longitudinally spaced locations in order to accurately locate thepoint at which the pipe is stuck.

The current procedure in determining the point at which a string of pipemay be freed is to take la series of readings in the pipe at lower andlower levels until a point is found where no readings can be obtainedwhich is indicative of the fact that the stress or strain at this pointcannot be varied due to the stuck condiion of pipe above his point.vGenerally these readings will diminish from full 3,039,544 Patented June19, 1962 ICC readings in totally free pipe to zero at some point wellbelow the top of caved in formations or settlings that are binding thepipe. This is due to the fact that torque or tension is transmittedthrough the top portion of the loose material around the pipe and acertain amount of free travel is established in this loose formation bythe usual working of the pipe by the operator in lan eifort to free thepipe. This free travel is often misleading as to the -true degree ofstuckness of the pipe and often results in the pipe being backed olf orcut at a depth well below the top of the formation that is binding it.When this happens it is often impossible to pull the freed portion ofpipe from the bore hole necessitating a 4second cut or back ofi, or, ifthe freed portion can be pulled out of the binding material the topportion of the iis-h may be filled by this material falling into it andfuture iishing operations may be impeded.

In the inclinometer method, described more fully hereinafter, thiscondition of stress and strain transmitted through the loose formationis not so much a factor. Changes in tension and in the amount of torquepresent in free pipe will cause the pipe to repose in the bore hole indifferent conditions of convolutions =and/ or spirals. This isespecially true if the free pipe in one condition is under -aconsiderable tension as shown in FIGURE 1A, and another condition ofbeing relaxed with weight of upper sections bearing down on it as shownin FIGURE 2A. Normally, under tension the pipe would reside on the lowside of the bore hole (all -bore holes have some deviation from a truevertical) and generally conform to the contour of this low side. Whenunder compression, the pipe would bow out at intervals from this lowside and rest approximately against the opposite wall of the bore hole.This produces a series of convolutions or curves in the pipe 4thatcauses the pipe at one point to have less inclination and at anotherpoint to have more inclination than it had when under tension, lf thereis loose formation surrounding the pipe it cannot have the freedom ofside to side movement to produce changes in inclination because it wouldrequire a very considerable force to produce side movement of the pipeagainst the restraining forma- -tion Eand this force is not sufiicientsince it is derived from the weight of upper sections applied at therelatively small angles in the pipe in relation to the bore hole.

Thus, if an inclinometer log is run of a section of pipe, part of whichis free and part stuck, under conditions of tension and compression,there will be a sharp change between the character of the two logs atthe point Where the binding formation begins, which is the desirablepoint at which to attempt a `cut or back o'if of the pipe. This changein character of the inclinometer logs in f-ree pipe can be induced by achange in the amount of torque applied since twisting a string of pipewill cause it to assume a spi-ral condition with resultant changes ininclination at different points.

The inclinometer instrument may be used to make readings at selectedpoints like instruments currently in use, but the amount of change indeviation will vary from point to point. Any reading, however, willindicate that the pipe is free and readings can be checked at laslightly different depth to avoid points where the inclination of thepipe does not change appreciably between conditions of tension orcompression.

The present invention has for an important object the overcoming of theabove disadvantages of the methods heretofore employed in logging thevariations and inclinations of a well bore or of a pipe located in sucha bore, by the use of an improved method of and means for continuouslymeasuring the inclination of the bore or pipe throughout its length.

Another object of the invention is to provide a method for accuratelylocating the stuck portion of a pipe which is stuck in a well bore.

A further object of the invention is to provide an inclinometer ofimproved construction and sensitivity, for use in measuring very smallvariations in inclination from the vertical.

Another object of the invention is the provision of an inclinometerwhich is electrically operated and by which a continuous record or logof the changes in inclination of a well bore or of a pipe locatedtherein may be made.

A further object of the invention is to provide a method of accuratelylocating the stuck portion of a string of pipe stuck in a well borewhich comprises making a continuous record of the amount of deviation ofthe pipe from the vertical throughout a substantial length of the pipeincluding a portion of the pipe at the location where the pipe is stuck,applying a force to the pipe to change the inclination of the freeportion of the pipe, making a con tinuous record of the deviation of thepipe from the vertical throughout said length of the pipe, and comparingthe two recordings to locate a region in the pipe where the inclinationof the pipe remains substantially unchanged.

Another object of the invention is to provide a method for locating thestuck portion of a string of pipe stuck in a well bore which comprisesmaking a continuous record of the variation in inclination throughoutthe length of the pipe including a portion of the pipe at the locationwhere the pipe is stuck, while the pipe is in a relaxed condition,exerting a pull on the upper end of the pipe to change the inclinationof the pipe throughout the free portion of the pipe, making a continuousrecord of the variation in the inclination of the pipe throughout saidlength of the pipe, while maintaining the pulling force on the upper endof the pipe, and comparing the two recordings to locate the portion ofthe pipe in which the inclination remains substantially unchanged.

A further object of the invention is to provide a method of placing awell pipe in condition to be disconnected which includes determining thevariations in inclination of the pipe throughout a portion of the lengthof the pipe to determine the condition of stress in the pipe in saidportion and applying a force to the pipe to place the pipe in a desiredcondition of stress.

A still further object of the invention is to provide an inclinometer ofsimple design and rugged construction whose sensitivity and accuracy issubstantially unaifected by the extreme conditions of hard usage towhich instruments of those characteristics are likely to be subjectedwhen used in well logging operations.

The above and other objects and advantages of the invention may best beunderstood from the following detailed description constituting aspecification of the same, and considered in conjunction with theannexed drawings wherein- FIG. l is a fragmentary, partly diagrammaticview, illustrating the method and apparatus of the invention showing theinclinometer of the invention partly broken away and partly incross-section located in the well pipe in a well bore, the recordingmechanism employed therewith being shown diagrammatically;

FIGURE lA is a fragmentary, vertical, central, crosssectional view on areduced scale, of a portion of a well bore showing a well pipepositioned therein, and showing a location at which the pipe is stuck inthe well, the pipe being shown in the position which it occupies duringone stage of the method of the invention;

FIGURE 2 is a fragmentary front elevational View of a portion of a chartshowing a typical form of the continuous record made by the method andapparatus of the invention, and indicating the variation in theinclination from the vertical of a well pipe in a well bore;

FIGURE 2A is a view similar to that of FIGURE lA, showing the typicalvariation in the inclination of a well pipe corresponding to therecording of FIGURE 2 during another stage of the method of theinvention.

FIGURE 3 is a fragmentary, vertical, central, cross sectional View, on asomewhat enlarged scale, of a portion of a well bore, showing a wellpipe therein with the inclinometer of the invention in an operableposition in the pipe, the pipe being shown partly broken away and partlyin cross-section;

FIGURE 3A is a fragmentary, front elevational view on a somewhatenlarged scale of a portion of a chart showing a typical recordingindicating the variations of the inclinometer of the invention as theinclinometer passes downwardly through the pipe, illustrated in FIGURE3; and

FIGURE 4 is a vertical, central, cross-sectional view, on an enlargedscale, showing details of construction of the operating elements of theinclincmeter of the invention.

Referring now to the drawings in greater detail, the method andapparatus of the invention are particularly useful in connection withthe drilling and operation of wells, such as oil wells, the bore of sucha well being indicated at B, which bore may be provided with a casing orliner C, extending downwardly from its upper end throughout a portion ofthe bore, and having an inner pipe or tubing T, of substantially smallerdiameter than the bore, which extends below the lower end of the casingC and which is illustrated as being stuck in the well bore, as by thecaving of the surrounding formation as shown at F, or the accumulationof drilling mud, sand, or the like, in the bore about the exterior ofthe pipe.

Under these conditions, it is desirable to accurately locate the zone inthe well bore in which the pipe is stuck, so that the pipe may be cut ordisconnected at a point above the stuck portion to permit the portionabove to be removed from the bore and the subsequent carrying out ofwashover operations by which the stuck portion of the pipe may berecovered from the well.

The apparatus by which the method of the invention is carried outcomprises an inclinometer enclosed in a suitable housing 10, connectedat its upper end to the lower end of a cable l2, by which theinclinometer may be lowered into the well pipe, and which is operated bysuitable winding mechanism 14 rotatably mounted in any convenient mannerabove the upper end of the well. The cable 12 is of the conductor linetype having one or more suitably insulated conductors therein by whichelectric current may be supplied to the inclinometer and through whichcurrent may iiow to suitable recording mechanism by which a continuousrecord of variations in the inclination of the well pipe may berecorded.

The inclinometer mechanism of the invention, as best seen in FIGURES land 4 includes an elongated tubular element 16 located in the housing 19and whose upper end 18 is closed and whose lower end extends into theupper end of an open receptacle 20 supported in the bottom of thehousing. The lower end of the tube 16 opens into the interior of thereceptacle 20 in spaced relation to the bottom of the receptacle and thetube and receptacle contain a column of `a heavy liquid, preferablymercury, whose upper end is located rat a predetermined level 22 in thetube caused by the pressure of air in the housing acting Vupon thesurface of the liquid in the receptacle. The housing 10 may becompletely closed Iand `sealed to maintain the pressure in the housingat any desired pressure and to prevent variations in the pressure of theexternal atmosphere from causing changes in the effective length o-f thecolumn of liquid. An induct-ance coil 24 surrounds the tube near itsupper end and within the tube a core 26 of magnetic material such asferrite or other suitable material having a high magnetic permeabilityis movably positioned in contact with the upper end of the mercurycolumn in position for longitudinal movement in the tube relative to theinductance or tank coil 24 to vary the inductive eect of this coil in anoscillator circuit in accordance with the longitudinal movement of theinductor in the tube. The coil 24 is connected as by means of`conductors 28 into an electrical circuit including an oscillator 30 ofconventional construction, located in the upper end of the housing Il)and is in turn connected by the conductors of the cable 12 to therecorder mechanism at the surface.

The recorder mechanism may be of usual construction including a couplingtransformer 32, having a primary winding 34 of low impedance connectedin circuit with the oscillator 3ft, through the conductors of the cable12, and with a suitable source of direct current supply, such as thatindicated at 36, and having a secondary winding 33 which is connected incircuit with a receiver 40 Whose output is supplied to an electricalrecorder 42 of usual construction, which includes a chart or tape 44upon which the record is made.

The oscillator 30 is constructed to generate an alternating current at afrequency which is determined by the size of the capacitors in theoscillator and the inductance of the tank coil 24 when direct current issupplied to the oscillator from the source 36 through the primarywinding 34 of the transformer 32 and through the conductors of the cable12. The frequency of the current generated by the oscillator may be ofthe `order of 40 kilocycles and this alternating current is transmittedthrough the cable 12 to the coupling transformer 32 and through thetransformer and bypass condensers, not shown, to ground land thus backto the oscillator. The alternating current from the oscillator issuperimposed on the direct current and generates an alternating currentof the same frequency in the secondary 38 of the coupling transformer.The direct current passing through the primary has no effect on thesecondary, So that -a separation of the alternating current from thedirect current is effected by the coupling transformer in the receiver40, shown in FIGURE l. There is another oscillator (not shown) providedin the receiver whose function is to provide a reference frequency whichmay be controlled by the operator. This reference frequency ofoscillation may be set to equal the frequency being generated by theinstrument in the well. The receiver also includes a frequency mixingcircuit which produces no output as long as the frequency of theoscillator 30 and the frequency of the oscillator in the receiver lareequal, but when one of these frequencies changes, there is generated inthe mixer device an alternating potential whose frequency is thedifference between the two frequencies being fed into the device. rfhisis known as a beat frequency. This .beat frequency is amplified in thereceiver and fed through a rectifier network in the receiver whichproduces a direct current output from the receiver whose magnitude isdirectly proportional to the beat frequency. The output from thereceiver is fed directly into the recorder 42, shown in FIGURE l, whichproduces a record on the chart 44 indicating variations which take.place in the frequency of the current from the oscillator 30. Thus, aslong as the frequencies of the currents from the oscillator 30 and thosefrom the oscillator in the receiver remain the same, the record on thechart 44 will be a straight line, but upon the occurrence of a Variationin the frequency of the current from the oscillator 3), the direction ofthe line on the chart will be changed accordingly, indicating adeviation of the inclinometer from the vertical.

In practice, the inclinometer is suspended vertically before lowering itinto the well and the receiver 4t)` is adjusted to produce Zero beatfrequency or zero output, 'and the recorder, likewise is adjusted toindicate zero, so that the pen 46 of the recorder, shown in FIGURE l,will make a straight line longitudinally moving on the chart 44. In thisposition of the inclinometer, the effective length of the mercury columnsupporting the core 26 will be shortest, and the core will be at itsfarthest point of movement relative to the tank coil 24; causing theinductance of the tank coil to be at a minimum and the frequency of theoscillator 3@ to be at a maximum.

In this condition of the apparatus, any variation of the inclinometerfrom the vertical, regardless of the di- 6 will produce a decrease inthe frequency of the current from the oscillator 30 due to movement ofcore 26 toward the coil 24 caused by a change in the effective length ofthe mercury column, causing the pen of the recorder to move laterally onthe chart 44 to indicate such change of inclination.

It will be apparent that by varying the impedance in the electricalcircuit between the receiver 40 and the recorder 42, the instrument maybe calibrated to produce more or less `lateral movement of the pen 46upon the occurrence of a predetermined amount of change in theinclination of the inclinometer. For example, the rst calibration maybesuch as to produce a full scale deflection of the recorder for adeviation of the inclinometer of l degree. Subsequent calibrations maybe made requiring a 2 degree inclination in the inclinometer'to producefull scale deflection of the recorder or the instrument may becalibrated to require 3 or 4 degrees or more inclination of theinclinometer to produce full scale deflection of the recorder to adjustthe recorder to record the maximum deviation likely to be encountered ina well bore.

lf this inclinometer is run in a -bore hole or through a string of pipein a bore hole it is possible to record deviation from the vertical as afunction of depth as indicated in FIGURE 2. Such a recording will showsudden changes in deviation in a bore hole, commonly called dog legs,which might be missed by a directional sur- Vey made at intervals in thebore hole.

The change in the inclination of pipe as before described is necessarilysmall because of the relatively close proximity of the walls of the borehole to the pipe. This condition will vary as will the forces causingchanges in inclination but in general it may be stated that the changewill be of the order of l degree to 2 degrees or less. In some instancesof heavy sections such as drill collars, the change may be as small asone-third of one degree. It is apparent, therefore, that an inclinometermust be sensitive and have a high degree of resolution to successfullyrecord such changes in deviation. As before mentioned the most sensitivecalibration sitting should produce a full scale deflection of therecorder for a change of only one degree. On such a scale, 1/3 of onedegree change (or 20 minutes) will appear as 1/3 of full scale which iseasily discer'nable.

At the point where a string of pipe is stuck, it may be found that thedeviation from the vertical is relatively large as for example 9degrees. If the sensitivity calibration step is set high enough forexample l0 degrees for a full scale deflection of the recorder, then 9degrees will appear on the chart on the extreme right, and if thevariations in deviation of the pipe were only 1A of one degree, then thechanges which can be recorded in inclinometer logs between theconditions of tension and compression will appear small in comparisonwith the full scale of the log.

To offset this condition, the beat frequency oscillator in the receivermay be adjusted in a direction to reduce the beat frequency an amountequivalent to say 8 degrees: then a reading of 9 degrees will appear onthe log in the same place as a l degree reading would before. This willcreate an artificial zero and then by using a sensitivity step of say 2degrees for full scale, it is possible to record differentialinclinometer logs to reveal positively small changes in inclination eventhough the total inclination of the string were large.

The inherent sensitivity of this device may be seen from the fact thatthe inductance of a tank coil of an oscillator whose natural frequencyis in the order of 40 kc. has a very profound effect on the oscillator.In other words, changes in the position of a tuning inductance withinthe tank coil will sharply change the natural frequency of oscillation.Specifically, a change of only .O01 inch either in or out of the tankcoil (shown in FIGURE 4) by the inductor will shift the frequency ofoscillation by as much rection of such deviation,

as 30 cycles. If an inclinometer tube 30 inches long is inclined ldegree from the vertical, the length of the column of 'mercury will beincreased .0045 inch, which will cause the inductor t'o move this amountinto the tank coil and will produce 4.5 times 30, or 135 cycles change.This will be more than 2 cycles change for each minute of change indeviation and easily falls within the previously described minimumrequirement of 1 degree for a full scale deliection of the recordingequipment.

The inciinometer instrument will be sensitive to changes in the internaldiameter of the pipe. In FIGURE 3, the instrument moving down inside aninclined section of pipe will be disposed on the low side and the noseof the instrument will be deected toward the center of the pipe onreaching an internal reduction in diameter, such as may be caused by acoupling 50, thus causing a momentary increase in `deviation and a kickor jog on the inclinometer log away from Zero. The reverse will happenas the instrument passes through such an internal reduction back intothe original pipe size, as indicated at 54. Thus internal upset pointswill show as a kick, followed by reversal. Reduction in pipe size willshow as an outward curvature of the line of the recording and anincrease in pipe size will show as an inward curvature of the line.

The inclinometer instrument may be used to find the condition at whichtension and compression are equal at a given point in a string of pipeabove the stuck point. If the instrument is positioned at a point whereit had been observed (from logs or static readings) that a change ininclination occurred between tension and compression in the pipe andstarting with a relaxed condition (compression) to slowly raise thestring of pipe at the surface until a change in reading is firstobserved; this rst show of change will be at the moment tension iirstarrived at the location of the instrument and will be a neutral pointand will give an operator suircient and accurate information for backingo the pipe at this point.

It will, of course, be apparent that any suitable device, such as adirect current meter may be substituted for the recorder mechanism 42when it is desired merely to indicate to the operator when the stuckpoint is reached without making a record of the variations ininclination of the pipe.

In carrying out the method of the invention, the inclinometer is loweredinside of the string of pipe whose variation in inclination it isdesired to determine and current is supplied to the inclinometer in themanner previously described, and the changes in inclination of theinclinometer are recorded as we show above, with the pipe in a relaxedcondition in the bore. As the inclinometer is lowered in the bore, thedeviation of the instrument from the vertical will be continuouslyrecorded on the chart 44. When the inclinometer reaches the bottom, anupward pull may be exerted on the string of pipe, which will tend toreduce the variations in inclination throughout the free portion of thestring above the stuck portion, and the inclinometer may be movedupwardly through the pipe while the pipe is maintained in this conditionto make a second recording of the variations in inclination. Bycomparing the two recordings thus produced, it will then be possible toaccurately locate the portion of the pipe which is stuck in the bore andthe portion which is free above the stuck portion, to determine wherethe pipe shall be disconnected or cut olf to permit the removal of thefree portion. During the carrying out of the method in this manner, itwill be apparent that the stuck portion of the pipe will be held againstbeing affected by the upward pull exerted on the string, so that thevariations in inclination of the stuck portion will remain substantiallythe same While the variations in the inclination of the free portion ofthe pipe will be changed, so that the location where the free portion ofthe pipe joins the stuck portion may be accurately located.

It will be apparent that under some conditions, the location of thestuck portion of the pipe may be determined by a single pass of theinclinometer, either with the pipe in a relaxed condition, or under thetension produced by an upward pull on the string. It will also be seenthat the amount of upward pull exerted on the string need not besuicient to place the entire length of the free portion of the pipe intension, since the method ofthe invention does not depend upon thetension or compression to which the pipe is subjected, but only upon thechange in inclination resulting from a change in the downward forceexerted on the pipe.

rThe invention is disclosed herein connection with a certain specificembodiment of the apparatus employed and procedure in carrying out themethod, but it will be understood that these are intended by way ofillustration only and that various changes may be made in theconstruction and arrangement of the parts of the apparatus as well as inthe particular steps of the method, within the spirit of the inventionand the scope off the appended claims.

Having thus clearly shown and described the invention, what is claimedas new and desired to secure by Letters Patent is:

l. The method of locating the stuck portion of a well pipe Strick in awell bore in which the free portion of the pipe above the stuck portionis in a condition of stress causing inclination of said free portion ofthe pipe above the stuck portion comprising, measuring variations in theinclination of the pipe along the pipe, and concurrently measuring thedepth at which said measurements are made whereby the stuck point can belocated as lbeing that portion of the pipe below which no variations inthe inclination of the pipe are noted.

2. The method of locating the stuck portion of a well pipe stuck in awell bore comprising, placing the pipe above the stuck portion in astress causing inclination of the free portion of the pipe above thestuck portion, measuring variations inthe inclination of the pipe alongthe pipe, and concurrently measuring the depth at which saidmeasurements are made whereby the stuck portion can be located as Ibeingthat portion of the pipe below which substantially no variations aremeasured.

3. The method of locating the stuck portion of a well pipe stuck in awell bore comprising, measuring the variations in the inclination of thepipe along the pipe while the pipe is one condition of stress,concurrently recording the depth at Iwhich the inclination measurementsare taken, applying a force to the pipe suf'ricient to cause the freeportion of the pipe above the stuck portion to assume inclinationsdifferent from those existing when the first measurements are made,again measuring the variations in the inclination along the pipe whileconcurrently recording the depth at which the secc-nd inclinationmeasure- `ments are taken, and comparing the first and secondmeasurements whereby the stuck portion is located as being the portionbelow which no change of inclination occurred in either measurement.

4. The method of claim 3 wherein the step of applying a force to thepipe includes the steps of applying a longitudinal 'force to the pipe.

5. The method `of claim 3 wherein the step of applying a force to thepipe includes the step of applying a torque to the pipe.

6. The method of locating the upper stuck point of the stuck portion ofa Well pipe stuck in a well bore comprising, measuring variations in theinclinationy of the pipe along the pipe While the pipe is in onecondition of stress, concurrently recording the depth at which theinclination measurements are taken, applying at the surface a force tothe pipe sufficient to cause the free portion of the pipe above thestuck point to assume inclinations different from those existing whenthe lirst measurements are taken, again measuring the variations ininclination along the pipe while concurrently recording the depth atwhich the second inclination measurements are taken, and comparing thefirst and second measurements whereby the upper stuck poin-t is locatedlas being the point below which no change in inclination of the pipeoccurred between the rst and second measurements.

7. The method of substantially neutralizing the stress in a tool jointof known position above the stuck portion of a well pipe stuck in a wellbore preliminary to disconnecting the tool joint comprising, placing aninclinorneter in the pipe adjacent said tool joint, and applying =aforce to the pipe to remove the stress from the pipe at the tool jointuntil the inclination of the pipe changes thereby indicating that thestress in the tool joint is substantially removed.

8. The method of substantially neutralizing the longitudinal stress in atool joint of known position above the stuck point in a well pipe stuckin a well bore preliminary to disconnecting the tool joint comprising,placing an in clinometer in the pipe adjacent said tool joint, applyinga llongitudinal `force to the pipe in a direction to remove the`longitudinal stress `from the pipe at the tool joint until theinclination of the pipe changes thereby indicating the longitudinalstress in `a tool joint is substantially removed.

9. The method of locating the position of variations in the internaldiameter or" a pipe comprising, moving an inclinometer through and incontact with the pipe thereby measuring the inclination of the pipe,concurrently measuring the position of the inclinometer in the pipe, andnoting the variations of the inclination of the inclinorneter withreference to the variations of the inclination of the pipe therebylocating the positions of the variations in the internal diameter of thepipe.

10. The method of locating the positions of variations in the internaldiameter of a pipe in a well bore comprising, moving an inclinometerthrough an in contact with the pipe, concurrently measuring variationsin the inclination of the pipe, concurrently measuring the position ofthe inclinometer in the pipe, and noting the variations of theinclination of the inclinometer with reference to the variations `of theinclination of the pipe thereby locating the positions of variations inthe internal dameter of the pipe.

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